CHROMOSOME (color body, so called from its affinity for certain stains), a body of peculiar protoplasm, in the nucleus of the cell. Each species has its own characteristic number; the cells of the human body contain 24 chromosomes each. CONGENITAL (with birth), present at birth. The term fails to distinguish between traits which are actually inherited, and modifications acquired during prenatal life. In the interest of clear thinking its use should be avoided so far as possible. CORRELATION (together relation), a relation between two variables in a certain population, such that for every variation of one, there is a corresponding variation of the other. Mathematically, two correlated variables are thus mutually dependent. But a correlation is merely a statistical description of a particular case, and in some other population the same two variables might be correlated in a different way, other influences being at work on them. CYTOLOGY (cell word), the study of the cell, the constituent unit of organisms. DETERMINER (completely end), an element or condition in a germ-cell, supposed to be essential to the development of a particular quality, feature, or manner of reaction of the organism which arises from that germ-cell. The word is gradually falling into disuse, and "factor" taking its place. DOMINANCE (mastery), in Mendelian hybrids the capacity of a character which is derived from only one of two generating gametes to develop to an extent nearly or quite equal to that exhibited by an individual which has derived the same character from both of the generating gametes. In the absence of dominance the given character of the hybrid usually presents a "blend" or intermediate condition between the two parents. DYSGENIC (bad origin), tending to impair the racial qualities of future generations; the opposite of eugenic. ENDOGAMY (within mating), a custom of some primitive peoples, in compliance with which a man must choose his wife from his own group (clan, gens, tribe, etc.). EUGENIC (good origin), tending to improve the racial qualities of future generations, either physical or mental. EUTHENIC (good thriving), tending to produce beneficial acquired characters or better conditions for people to live in, but not tending (except incidentally and indirectly) to produce people who can hand on the improvement by heredity. EVOLUTION (unroll), ORGANIC, the progressive change of living forms, usually associated with the development of complex from simple forms. EXOGAMY (out mating), a custom of primitive peoples which requires a man to choose a wife from some other group (clan, gens, tribe, etc.) than his own.